Email systems facilitate the exchange of electronic mail over a network, such as a LAN (local area network), WAN (wide area network), or public network (e.g., Internet). Most people are familiar with traditional computer email systems based on a client server model. With intense need for global communications, email systems migrated more towards the thin client model running inside a browser. These thin clients are typically constructed with just enough functionality to enable access to the server computer over a network. Browser-based email systems are well suited for thin clients. The client mailbox is maintained at a server and the client accesses the mailbox using standard Web protocol.
With current web based email systems, a validated user can login to the same account multiple times, from multiple locations. This can cause problems with the mail system databases when the same data is viewed and manipulated from multiple active locations with no real-time checking or blocking of subsequent login attempts when an existing validated login session is active at some other location. Some existing solutions expire the earlier active session instead of blocking a subsequent session.